A New Method for Eliminating Background Signal Drift to Improve the Detection Precision in Continuous Harmonic Detection
ZHAO Ying1, ZHAO Xue-hong1,2*, WANG Zhe1, ZHANG Rui1,3, WANG Yan1
1. Collegy of Precision Instrumonts and Opto-Electronics Eningeering, Tianjin University, Tianjin 300072, China 2. Tianjin Key Laboratory of Biomedical Detecting Techniques & Instruments, Tianjin 300072，China 3. College of Electronic Information and Automation, Tianjin University of Science and Technology, Tianjin 300222, China
Abstract：To overcome the second harmonic background signal drift in gas continuous detection based on tunable diode laser absorption spectroscopy(TDLAS), a new method of background elimination was proposed by changing center current of the laser. This method can eliminated the effects of background signal drifting on concentration inversion. Based on the wavelength modulation theory, the theoretical expression of the second harmonic of the background signal is derived. In addition，the second harmonic background signal components and the factors that affect it are described. In different working temperatures, the relationship curve between thelaser current and output light intensity. In the process of continuous detection, we analyzes the feasibility ofchangingthe laser center current extraction of background signal. Combined with the principle of the background signal searching, the LabView flow chart was designed to search background center current. Ammonia(NH3) was detected by the TDLAS experimental system, which demonstrated the feasibility of the new method. The range of experiment parameters and the range of background center current searches were determined, in the situation that there was only one absorption line in the full laser workspace. The experimental results showed that this method realizes background signal extraction, reduces the error of concentration inversion and the effects of concentration inversion bybackground signal. Thus it improved the detection accuracy of the concentration. In the continuous detection experiment, the standarddeviation of inversion concentration reduced from 2.688 3 to 1.856 1, which demonstrated that the degree of dispersion of detected concentration is reduced, even eliminate the effects of background signal drifting on concentration inversion and the accuracy of detection is improved. This method provides an effective background drifting elimination approach for improving the detection accuracy of the concentration.
Key words：Stunable diode laser absorption spectroscopy(TDLAS);Harmonic signal detection;Background elimination;Second harmonic
赵 迎1，赵学玒1，2*，王 喆1，张 锐1，3，汪 曣1 . 一种用于谐波检测过程中消除谐波背景方法的研究 [J]. 光谱学与光谱分析, 2015, 35(11): 3224-3229.
ZHAO Ying1, ZHAO Xue-hong1,2*, WANG Zhe1, ZHANG Rui1,3, WANG Yan1 . A New Method for Eliminating Background Signal Drift to Improve the Detection Precision in Continuous Harmonic Detection . SPECTROSCOPY AND SPECTRAL ANALYSIS, 2015, 35(11): 3224-3229.
